This invention relates generally to the processing of canned beer, and is particularly directed to eliminating the problem of can buckling of the attached top during the pasteurization of beer.
It is conventional to pasteurize canned beer by conveying filled and sealed cans of beer to a heat treatment station at which the beer is pasteurized. This heat treatment is intended to inactivate whatever yeasts remain in the beer to prevent further fermentation.
During such heat treatment, carbon dioxide is released from the beer and adds to that already at the headspace of the can, thereby raising the internal pressure on the can to the greatest degree it will normally experience. This high pressure can buckle the shape of the can, particularly its top and bottom which are the weakest areas of the can in this respect. To prevent such buckling, a much thicker metal sheet is used to strengthen the can's top and bottom, compared to the sidewall. However, this increases the cost of the can.
Similar problems with can buckling have long been known in industries other than beer canning. In some instances, a food-containing can is mated with at least two and up to four shape-retaining pieces which are held by vice-like members during the heat treatment. Such a solution has not found acceptance in the beer canning industry, however, because it would require major changes within the existing conventional pasteurizer, such as: new equipment for placing, holding, and conveying all the close-fitting shape-retaining pieces over each beer can, and; new heat transfer equipment for heating beer cans that are surrounded by these pieces. Such changes are not conveniently adaptable to the conventional pasteurizer which is designed to heat and convey each beer can as part of a several-foot-wide,standing group by using overhead hot-water sprays and walking beam conveyors, respectively.
Thus, prevention of can buckling has only been achieved by using a much thicker gauge metal sheet for the ends of beer cans, an undesirable solution.